Avanti: Project Automatic Overdrive by Bill Henderson, AOAI Pennsylvania Member, [email protected]
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Avanti: Project Automatic Overdrive By Bill Henderson, AOAI Pennsylvania Member, [email protected] I hadn’t owned my Avanti very long, when on an early summer morning drive on the Interstate to a club event my wife commented, “It doesn’t seem happy.” I could hardly argue with her. In fact, I was thinking the same thing. It was a hot day. Keeping up with traffic at 75 MPH the car ran smoothly but the engine was screaming like an over‐ revved sewing machine. The tachometer read 3300 RPM, and I kept wishing I had another gear to shift to. Further, by the time we had reached our destination more than an hour later, we were both drenched with sweat, as the footwells and console were radiating heat worthy of a smelting oven. The chrome shifter was so hot that it couldn’t be touched without risking blisters. Even the air coming in the floor vents offered no relief as it was scalding hot, passing as it did through the oven–like cowl and past combination of summer driving, today’s faster the firewall before reaching our feet. “That car highway speeds, the high rear gears, the ancient needs air conditioning,” said my wife with some transmission and the fiberglass floor and firewall annoyance as we joined the party, our backs soaked made me realize that I needed to address the issue if with perspiration. I frowned. Installing air I was going to enjoy this car for years to come. conditioning on an R2 is a highly custom proposition, Besides insulating the floor and firewall, I needed to and I knew deep down that no auto air conditioner reduce the engine speed on the road. would be able to overcome that inferno. I realized the answer had to start with addressing the source It was time to consider a modern automatic of that heat. Further, just hearing that screaming overdrive transmission swap. engine was an assault to my ears; 3.73 rear gears couldn’t have helped, and the 10 MPG I got on that The Issue of Originality trip was surely an additional result. This isn’t the first time I have considered doing a transmission swap. Some years ago I converted my The pace on the road was surely slower in North trusty V8 Hot Rod 1966 Mustang from a manual Ford Carolina where this car was sold new in 1963. There four speed to a 5‐speed Tremec overdrive, and I can were few Interstates and more country roads, and attest that it has made a world of difference in my likely this bright red Automatic Power‐Shift enjoyment of that car. When on the highway, I smile equipped Avanti wasn’t used to commute great as I occasionally shift it from fifth back down into distances in heavy traffic. But even at slower fourth just to hear it howl, reminding myself of the speeds, long trips in the southern climate would wise choice I made. But I had never attempted to have been downright uncomfortable, though swap automatic transmissions on a car before, and frankly, we expected less of our cars back then. The the thought of trying to make any modifications to an all‐Studebaker powertrain was a bit intimidating occurs only in 4th gear, and when it kicks in, RPMs to me. drop by another 100 or so. It actually feels like a bonus 5th gear. Besides saving gas, this feature While I wouldn’t likely change the engine in my lessens the generation of heat by stopping slippage. Avanti to brand X (and I know some do), somehow it Proper attachment of a 12V connection to the seemed completely OK to me to swap out the transmission engages lockup, and is essential for its transmission; hidden beneath the floor and behind long life. the engine as it is, who would know besides me? I’ll admit that I am not a restoration purist, while I like GM 700‐4R GM 200‐4R to keep outward appearances stock‐looking; I have Description 4‐speed automatic 4‐speed automatic made adaptations on all of my collector cars for with lockup torque with lockup torque converter in converter in safety. All have disc brakes, dual master cylinders, overdrive, non‐ overdrive, non‐ electronic ignitions and radial tires, and brighter computer controlled, computer brake lights, for example. aggressive first gear controlled, more with fast shift into evenly spaced I have found that generally Studebaker people are second, Chevrolet gears, Universal much less bothered by modernization and bolt pattern. Can be GM bolt pattern. “built” to handle Pre 1986 units had adaptation of their cars than most other groups in extreme drag strip reputation of being the collector car hobby. Perhaps it is our need to use. Avoid early 27‐ less durable, but adapt to survive, since unlike owners of Mustangs spline output shaft rebuilt units and Camaros, we cannot go through a catalog and generally have all upgrades made. order practically every part of our cars brand new. Or maybe we are just more fun. Anyway, the way I Original Chevrolet 1982 to 1982‐1990 GM see it, old cars are meant to be driven, and anything Application 1992 Cadillac, Pontiac, Buick , Olds, one can do to make them more fun to drive, safer on Chevrolet the road and easier to maintain, the better. Requires Yes No modification to Transmission Choices Avanti floor and A major project like this one calls for some careful header pipes research. I spent more than six months researching Studebaker Yes Yes and considering my alternatives, compiling as much engine adapter plate available? data as I could from the Internet and print Gear ratios, 1st 3.06, 1.62, 1.00, .70 2.74, 1.57, 1.0, .67 publications, both Studebaker‐related and not, to through 4th see what success and failures others had found. Availability Excellent Good Approximate $1365 plus freight $1465 plus freight The two most documented choices for adapting an Cost, with “stage 1” “stage 1” Automatic Overdrive (AOD) to the Studebaker 289 Torque remanufactured remanufactured V8 are clearly the GM 700‐4R and 200‐4R. These are converter transmission transmission both pre‐computer controlled AOD transmissions, New driveshaft Yes‐ shorter Yes – longer meaning that they are easier to attach to the required? Avanti’s pre‐computer controlled engine than a Reputation for When properly built, When properly strength and both units are plenty built, both units are newer AOD transmission. The only means of reliability durable for this job. plenty durable for communication between engine and transmission is If buying one used this job. If buying the Throttle Valve cable, which connects between look for a later, 30‐ one used look for a the carburetor and the transmission. (See sidebar spline model. 1986 or later model near the end of this article) I decided that the 200 was the better choice for me. Both transmissions feature a lockup torque Besides the reason that the gears’ spacing and ratios converter, which allows the engine to direct‐connect seem to have better owner reviews, the fact that the to the driveshaft without any slippage. This usually unit is supposed to fit in the Avanti without cutting the floor or re‐bending exhaust pipes was a major convince them that it is not that difficult. Expect to factor for me. I don’t plan to thrash the car at the pay for two full days’ of labor for a job that does not drag strip; however the fact that the 200 was the include completely removing the engine as I have standard transmission for the Buick Regal V6 Turbo done. seemed to indicate that it wasn’t a lightweight. Further, I planned to buy a remanufactured unit, so I Removing the old would be assured that the internals were all Most will say that the far easier way to do this job is updated, properly assembled and working well, and from underneath, removing only the transmission would carry a guarantee besides. and torque converter while leaving the engine in place. I’d probably agree, as long as you have a way I chose to buy my transmission from Bowtie to raise the entire car at least 18 inches off the floor Overdrives in Hesperia, California, based on my and have a suitable transmission jack. Regular floor research and the many positive comments I jacks are not designed to balance an automatic encountered during my search. Aiding my decision was the fact that they are clearly accustomed to dealing with a hobbyist‐mechanic like me, one who knows his way around a shop and has good tools but who doesn’t install transmissions for a living. Their online guides alone are a gold mine of reference information during the selection process. (www.bowtieoverdrives.com) Myers Studebaker Parts provided the various important items needed to mate the GM Transmissions with the Studebaker engine. Jon Myers’ son Mike is the in‐house expert on this swap, and he willingly helped me by telephone several times during the conversion when I was unsure of myself. The same adapter plate works with both transmissions. (www.myersstudebaker.com) Do It Yourself Installation? I would rate this job as one that only the most confident do‐it‐yourselfer would try at home. While no true “engineering” is required of the installer, and all special parts have already been made, (excepting the carburetor Throttle Valve cable lever) considering the logistics of removing an engine or transmission, this is not an easy job. Several specialized tools are needed for this job, including an engine lift and/or a suitable transmission jack, and I wouldn’t try to do it without a good set of ½” sockets, some in large sizes, and a torque wrench.